Field of the Invention
This invention relates generally to an adsorbent coated biologically active support for use in biological processes for the purification of waste streams, as for example industrial and municipal waste waters and to products, apparatuses and processes for use of such media. More particularly, the present invention relates to coating compositions for use in preparing such support media. The coating compositions comprise a binder, an aqueous solvent and a suspension aid and an adsorbent material, capable of absorbing pollutants and promoting their subsequent biodegradation by microorganisms attached and immobilized to the support media. The coating composition may also include a settlement retardant, which prevent adsorbent from settling out of the coating formulation.
Another embodiment of the invention relates to an apparatus for removal of a desired material from a fluid stream comprising a vessel which comprises an inlet and outlet means for inflow and outflow of said fluid stream; wherein said vessel comprises a plurality of biologically active biomass support materials of this invention.
An additional embodiment relates to a method for the removal of a desired material from a fluid stream comprising the desired material; said method comprising contacting a fluid stream with a plurality of biologically active biomass support materials of this invention. It is noted that the various materials and methods of this invention described herein can be used to remove inorganic and organic materials from fluid streams.
There are several methods of applying an adsorbent to a substrate. Some of these include varied processes, such as heat treatment, solvent-slurry and binder attachment. In heat treatment process, a substrate is heated to a temperature at which it softens during which time carbon is mixed with the substrate material, which is then allowed to cool. Upon cooling the adsorbent is adhered/affixed on the substrate surface. Temperatures and heating time will vary with the choice of substrate and adsorbent. The support produced by the heat treatment process creates an essentially monophasic layer of adsorbent particle, at the surface of the support (See FIG. 10). Potential disadvantage associated with the heat treatment method include (i) heat deactivation of the adsorbent or inhibition of the adsorbent's ability to function as desired; (ii) diminution of the physical properties of the substrate (iii) loss of available surface area of the adsorbent for binding since a portion of the surface is actually bound to the substrate surface and (iv) agglomeration of adsorbent particles.
A solvent/adsorbent slurry can be applied to the substrate using conventional techniques. The substrate is dipped in the slurry or spray coated with the slurry and then dried. It is important that the adsorbent be affixed firmly to the substrate in an active state after any excess slurry and solvent are removed from the support. It should be noted that although we refer to the method as "solvent slurry" the solvent merely functions as a vehicle for dispersing the adsorbent in a fluid matrix or may soften the substrate surface and/or swell the substrate. After coating the substrate with the slurry, the solvent may be evaporated and recycled. Similar to the heat treatment process, the solvent-slurry method also creates a monophasic layer of adsorbent particles on the surface of the support since the solvent is substantially removed by conventional drying techniques. Disadvantages may also accompany the solvent slurry method. These include (i) solvent deactivation of the adsorbent or inhibition of the adsorbent's ability to function as desired; (ii) diminution of the physical properties of the substrate (iii) loss of available surface area of the adsorbent for binding since a portion of the surface is actually bound to the substrate surface (iv) required selection of a substrate, adsorbent and solvent which can be applied together to work in concert and (v) disposal of spent solvent. Although the solvent slurry method can produce a substrate with active adsorbent deposited thereon, there may be some tendency for the adsorbent material to leach out from the substrate over time.
Methods of attachment which employ binders are generally of two types: a slurry method or "two-step" method. In the "two step" method, (i) a layer of binder is applied to the surface of a substrate and allowed to begin curing (ii) one or more adsorbents are added to the binder/substrate surface and (iii) the binder is then allowed to cure fully. The two-step process can be found to be commercially unappealing because of two curing steps. Therein, the present invention focusses on the application of an adsorbent material to a substrate via a simplified coating treatment. The method of this invention comprises applying a slurry coating which comprises a binder, an adsorbent and solvent to a substrate; and allowing the slurry coating to dry. The slurry method deletes any need for an intermediate drying step, permitting large batch mode preparation of the supports.
As noted, the invention is also directed to processes and apparatus used in the removal of pollutants from fluid streams. Processes employing the biologically active supports of this invention exhibit excellent performance characteristics. An important benefit which flows from this invention is that our process is resistant to upset. Resistant to upset describes the ability of the process to reduce efficiently the contaminant level of waste streams having a relatively high level of contaminants to a desired level, preventing intermittent contaminant levels in the effluent above a desired level. For example, in certain preferred embodiments of this invention, concentration levels of organic pollutants in the feed stream can be as high as about 5000 parts-per million (ppm) which through use of the process of this invention can be reduced to levels as low as 1 ppm, or 0.1 ppm or for that matter 20 parts-per-billion (ppb). This advantage is of immediate and substantial economic benefit in that it obviates the need for time consuming and expensive pretreatment processes for reducing the amount of contaminant in the aqueous stream directly exiting the manufacturing process before introducing the stream into a bioremediation process. Our process provides for continuous treatment of a waste stream such that the concentration of pollutant in the effluent stream is maintained below EPA mandated levels. In addition, since our process can remediate relatively high levels of pollutants, the likelihood of a pollutant-containing waste stream deactivating the microorganisms, killing or hindering their pollutant-degrading ability, is significantly reduced.
Another advantage of preferred embodiments of this invention is that the biologically active supports can be used in a fixed bed reactor system to reduce relatively high levels of organic pollutants in aqueous feed streams to relatively low levels with the additional benefit of significantly less sludge formation than that from currently available systems, affording important advantages in sludge disposal costs.
Another unique advantage of this invention is that significant reductions in levels of organic contaminants contained in the effluent stream can be obtained with reasonable hydraulic residence times as compared to prior art processes as for example, the process described in U.S. Pat. Nos. 4,634,672 and 4,681,851. In certain most preferred embodiments of the invention, the level of effluent phenol in a phenol-containing aqueous waste streams can be reduced to concentrations as low as 20 parts per billion at hydraulic residence times as short at 24 hours. This is also not a trivial benefit especially in view of the low levels of various organic pollutants such as phenol in aqueous waste streams from industrial processes set by the Environmental Protection Agency and the economic requirement that these reduced levels be obtained over reasonable time periods.